The invention is directed to purification of unsaturated hydrocarbons. More particularly, the invention is directed to preparation of purified hydrocarbons resulting in low levels of reactive gases.
Low-level calibration standards including a relatively low concentration of the analyte of interest within a matrix gas are often made by diluting a pure gas of the analyte with the matrix gas. At low levels (<10 ppm), the calibration standard is essentially the matrix gas with an impurity in it, that being the analyte. As a result, any other impurities that were in the matrix gas will essentially be in the calibration standard at essentially the same concentration levels. This gives rise to a problem if the analyte is also present as an impurity in the matrix gas. For instance, it would be nontrivial to make a calibration standard such as 100 ppb of carbon monoxide (CO) in balance ethylene (C2H4) if there existed 150 ppb of CO in the C2H4 to begin with. In order to make such a mixture, the analyte concentration in the starting matrix gas would have to be less than in the finished calibration standard.
It is also possible that the impurities in the matrix gas may react with the analyte cause the calibration mixture to be unstable. As an example, hydrogen sulfide (H2S) is thermodynamically unstable in the presence of oxygen (O2), and given enough time, the H2S will react with the O2 to form hydrogen (H2). In summary, in the presence of particular impurities in a matrix gas, the analyte will react and the calibration standard will be degraded, which will give rise to problems when trying to produce low-level calibration standards. To eliminate such problems one should use highly purified matrix gases.
A common matrix gas is one containing one or more unsaturated hydrocarbons. Many solutions for purifying these matrix gases exist.
G. Baptista et al. proposed removal of oxygen and moisture from gases, but they do not offer solutions to purify unsaturated hydrocarbons. (“Experimental study on oxygen and water removal from gaseous streams for future gas systems in LHC detectors”, G. Baptista, M. Bosteels, S. Ilie, C. Schafer: CERN, Geneva Switzerland). Furthermore, they do not suggest methods for removing sulfur dioxide, carbonyl sulfide, carbon monoxide, or carbon dioxide from gases, much less from unsaturated hydrocarbons.
BASF Technical Bulletin “BASF Catalysts: FAQ on Catalyst R 3-11” discloses a tableted catalyst containing finely dispersed copper in an accessible, high surface area, pore structure designed for removal of oxygen, hydrogen, and CO from process streams. However, they do not offer solutions to purify unsaturated hydrocarbons. Furthermore, they do not suggest methods for removing sulfur dioxide, carbonyl sulfide, carbon dioxide or moisture from gases, much less from unsaturated hydrocarbons.
BASF Technical Bulletin “BASF Catalysts: R 3-11 G” discloses a tableted catalyst including highly dispersed and stabilized CuO (at approximately 35% wt.) on a silica support with special promoters to enhance activity and stability. It further discloses removal of of oxygen, hydrogen, and CO. However, they do not offer solutions to purify unsaturated hydrocarbons. Furthermore, they do not suggest methods for removing sulfur dioxide, carbonyl sulfide, carbon dioxide or moisture from gases, much less from unsaturated hydrocarbons.
BASF Technical Bulletin “BASF Catalysts: R 3-15” discloses a tableted catalyst including 40% wt. of CuO, 40% wt. ZnO, and 20% wt. Al2O3. It further discloses removal of oxygen, acetylene, carbonyl sulfide, hydrogen, and CO. However, it discloses removal of olefins catalytically if hydrogen is available. They do not disclose unsaturated hydrocarbon purification. Indeed, when hydrogen is available, olefins are catalytically removed. Furthermore, they do not suggest methods for removing sulfur dioxide, carbon dioxide or moisture from gases, much less from unsaturated hydrocarbons.
Thus, those skilled in the art will recognize that there is a need for a method to purify unsaturated hydrocarbons, including removal of moisture, oxygen, carbon dioxide, carbon monoxide and sulfur dioxide. They will also recognize a need for producing a purified unsaturated hydrocarbon gases so that low level gas calibration mixtures can be achieved.